hugin

Hugin is a panorama photo stitching program. Essentially, Hugin is a GUI frontend for Panorama Tools. Stitching is accomplished by using several overlapping photos taken from the same location, and using control points to align and transform the photos so that they can be blended together to form a larger image. Hugin allows for the easy creation of control points between two images, optimization of the image transforms, and much more.

One of only options for Linux (my 2 paid-for Windoze ones beat it by a hundred miles). Overcluttered interface, no simple workflow or obvious control over options. Last fight was 10 min and no result, PanoPro in Windows worked in 45 seconds. Hugin can do with some extreme UI streamlining, also its is slow-as heck.